$count

[AlexBlokh]

In recent release we've introduced $count API and I wanted to shine some light on why we decided to implement one.

We pursue SQL-likeness with Drizzle, yet sometimes pure SQL is just bad, this is how you'd do count with our query builder:

const res = await db.select({ count: sql`count(*)` }).from(users);
const count = res[0].count;

not that bad you might say, yet count type would be unknown, since we didn't explicitly tell our sql tag the type of a column, which would be

const res = await db.select({ count: sql<number>`count(*)` }).from(users);
const count = res[0].count;

That still wouldn't work, because PostgreSQL will return count as bigint and MySQL will return count as decimal which will be returned as string, so if we want something robust - we should do:

const res = await db.select({ count: sql<number>`cast(count(*)) as int` }).from(users);
const count = res[0].count;

// or alternatively, yet we don't recommend
const res = await db.select({ count: sql<number>`count(*)`.mapWith(Number) }).from(users);
const count = res[0].count;

These all the above are reasons why we sometimes introduce utilities like $count, we will be prefixing util function like this one with $ to separate them from query builder APIs

const count = await db.$count(users); // this returns number
const count = await db.$count(users, eq(users.name, "Dan"); // with filtering

we've designed it to be used as a subquery too:

const users = await db.select({
  ...users, // all users columns
  postsCount: db.$count(posts, eq(posts.authorId, users.id)),
  // ^ subquery, will be inferred as number
}).from(users);

this way you can easily filter out only users with at least one post

const users = await db.select({
  ...users,
  postsCount: db.$count(posts, eq(posts.authorId, users.id)),
}).from(users)
  .where((t) => gte(t.postsCount, 1));

and you can use it with our relational queries too:

const users = await db.query.users.findMany({
  extras: {
    postsCount: db.$count(posts, eq(posts.authorId, users.id)),
  },
});

[ryespresso]

@AlexBlokh This doesn't appear to work with planetscale driver even though the types say they do. Getting db.$count is not a function

[Sukairo-02]

@AlexBlokh This doesn't appear to work with planetscale driver even though the types say they do. Getting db.$count is not a function

@ryespresso could you create an issue with reproduction example?

[ryespresso]

@Sukairo-02 just do a simple $count on a table with planet scale driver.Typescript code will pass but you'll get db.$count is not a function when running the query

[AlexBlokh]

we did, it works just fine, that's why we ask for a reproducible example project

[hnh-zeal]

If you are using database replica, db.$count cannot be used. It will return db.$count is not a function.

I tried with db.$primary.$count. It went well for me.

[capaj]

I love the addition. It's indeed a bit too verbose without this.

@AlexBlokh have you considered adding this into the query builder API?

[AlexBlokh]

thank you!

yes, but we don't wanna touch RQB v1, going to land in RQB v2
btw, I expect RQB v2 land soon, we're finally up to speed with this track

[rgrullondev]

I'm getting a typescript type error.

Property 'fieldAlias' is missing in type 'MySqlCountBuilder<MySqlSession<any, any, any, any>>' but required in type 'Aliased<unknown>'

[rgrullondev]

I solved it, you need to set the .as('') to the name of the extra field.
So if the field is topicCount, you need to add .as('topicCount')

The example should be update to reflect that.
postsCount: db.$count(posts, eq(posts.authorId, users.id)).as('postsCount')

[ivan-kleshnin]

Will the support of this be added to a QueryBuilder? E.g. qb argument of a view / mat. view factory:

export let usersCountView = github.materializedView("users_count")
  .as(qb =>
    qb.$count().from(usersTable) // Property $count does not exist on type QueryBuilder
  )